A quick wiki search claims that Scotia Plaza is the deepest "The excavation reached a depth of 110 ft (33.5 m) which is the deepest excavation for a building in Canada's history." - wikipedia. Take that as you will. Shangri-La was the second deepest.

A quick wiki search claims that Scotia Plaza is the deepest "The excavation reached a depth of 110 ft (33.5 m) which is the deepest excavation for a building in Canada's history." - wikipedia. Take that as you will. Shangri-La was the second deepest.